This invention relates to a system for monitoring the degree of alertness of the driver of an automotive vehicle, and more particularly to such a system that utilizes the driver""s seated posture to determine when the driver is becoming drowsy.
A significant number of automobile accidents are caused by the driver of a vehicle being tired, drowsy, or otherwise insufficiently alert to safely operate the vehicle. Many methods have been proposed to detect signs that a driver is becoming drowsy and/or is not fully alert. Examples of such systems are those which detect the driver""s head tipping or nodding forward, those which detect an increased blink rate or the eyes closing, and those which detect the accuracy with which the vehicle is tracking within the lane in which it is driving.
It is known to install a pressure sensing device in the driver and/or passenger seat of an automobile to monitor the amount and/or the distribution of pressure exerted on the seat by a person or object occupying the seat. In some proposed systems, the sensor detects pressure at a plurality of points distributed over the surface of the seat, and the resulting pressure pattern is fed to an occupant restraint system controller. The controller uses the data to suppress and/or adjust the deployment of occupant restraints such as airbags. For example, the controller is able to distinguish between the patterns indicating a heavy occupant, calling for a relatively rapid and/or high-powered inflation of the airbag; a lighter occupant, calling for a slower and lower-powered inflation; and a child safety seat, calling for complete suppression of bag deployment. Such a system, using variable resistors as pressure sensors, is taught by U.S. Pat. No. 5,474,327.
It is an objective of this invention to provide a method and apparatus for monitoring driver alertness that reliably and accurately determine when the driver""s level of alertness has degraded to the point where the driver may not be able to operate the vehicle safely.
It is a further objective of this invention to provide a method and apparatus for monitoring driver alertness that utilizes a seat-mounted pressure sensor that may also provide occupant status information to an occupant restraint system controller.
In achieving these and other objectives, a preferred embodiment of the invention disclosed herein comprises a sensor array disposed in the driver""s seat to sense a pattern of pressure exerted by the driver""s body at a plurality of points distributed over the seat surface. The invention system further comprises a computer which receives pressure pattern data from the sensor array and determines a probable driver alertness level based upon changes in the pattern of pressure detected by the sensor array.
According to another feature of the invention, the sensor array may also be used to supply data to an occupant restraint system controller. For example, the sensor may provide information regarding the driver weight and seating position in order to allow the restraint controller to make restraint deployment decisions. Using the sensor for two purposes avoids the additional cost of providing a dedicated alertness sensor is avoided.
According to another feature of the invention, a method of monitoring the alertness of a driver is provided comprising the steps of measuring a first pressure pattern exerted by the driver on a plurality of points distributed over the seat surface at a first time, measuring a second pattern of pressure at a later time, and determining a probable driver alertness level based upon a comparison of the first and second patterns. According to a preferred embodiment of the invention disclosed herein, the sensor array comprises a plurality of variable resistors located in the seat bottom and the seat back. The sensor array detects pressure at a sufficient number of discrete points distributed over the seat surface to provide an indication of the driver""s posture at any particular moment. The computer which receives the pressure pattern data from the sensor array utilizes a neural network processing technique which enables it to determine the probable driver alertness level based upon changes in the driver""s posture over time. The alertness level determination may be based upon, for example, the assumption that a driver begins to slouch in the seat as he/she becomes tired and his/her alertness level decreases. Alternatively, the alertness level determination may be based upon variations in the rate at which the driver makes changes in his/her position in the seat. The neural network processing technique allows the system to xe2x80x9clearnxe2x80x9d a particular driver""s normal or natural posture and or rate of position changes, and make determinations about how changes from these normal values occur as the driver""s level of alertness change.